Means for and method of offset printing



March 1950 H. J. LUEHRS MEANS FOR AND METHOD OF OFFSET PRINTING Filed June 21, 194 6 Patented Mar. 7, 1950 MEANS FOR AND METHOD OF OFFSET PRINTING Hans J. Luehrs, Westerly, R. I., assignor to C. B. Cottrell & Sons Company, Westerly, R. I., a

corporation of Delaware Application June 21, 1946, Serial No. 678,425

4 Claims. 1

In web offset rotary printing presses designed especially for textile printing it has been customary to employ a dampening unit for each printing cylinder so that the moisture was applied directly to the surface of each of the printing cylinders. This method while satisfactory for printing on paper, parchment and cellophane tends to produce poor contours and incomplete color separations of the design on textiles, due to the heavy film of ink necessary for coverage and its required chemical composition, suitable for this material. Furthermore, .these presses were necessarily complex because of the number of dampening units employed and also were expensive to build. I

My invention consists in novel means for and method of web offset printing in which the moistening agent is applied directly to the surface of the offset cylinder by a single dampening unit, this single application of the moistening agent ensuring sharp contours and perfect color separation as well as materially simplifying the construction of the press and reducing its cost due to the elimination of more than one dampening unit.

A practical embodiment of my invention is represented in the accompanying drawings in which Fig. 1 represents in diagram a web offset five color non-perfecting rotary press;

Fig. 2 represents a somewhat enlarged detail view showing the dampening cylinder as having a raised moisture carrying surface and the printing cylinders as having raised ink carrying surfaces coacting therewith;

Fig. 3 represents a detail view of the dampening cylinder taken in the plane of the line III of Fig. 2, looking in the direction of the arrow;

Fig. 4 represents a detail view of the first printing cylinder taken in the plane of the line IVIV of Fig. 2, looking in the direction of the arrows; and

Fig. 5 represents a similar view of the second printing cylinder taken in the plane of the line V of Fig. 2, looking in the direction of the arrow.

The offset or transfer cylinder is denoted by I and its impression cylinder by 2. The web 3 is shown as passing between the offset and impression cylinders and also around suitable guide rollers 4.

The offset cylinder may be provided with any well known or approved surface capable of receiving the moisture and ink and transferring the same to the traveling web as it passes between the offset and impression cylinders.

In Fig. 1 I have shown five color printing cylinders 5, 6, l, 8 and 9 arranged around the offset cylinder I to their usual individual inking units being denoted by III, II, I2, I3 and I4 respectively. The dampening cylinder I5 of the single dampening unit I6 is shown in position t transfer its moistening agent directly to the surface of the offset cylinder I. In the present instance this dampening cylinder is shown in position to directly moisten the surface of the offset cylinder I at a point between the web 3 and the first printing cylinder 5 so that in offset printing the surface of the offset cylinder is continuously moistened each revolution before it is inked by the printing cylinders.

In Figs. 2 to 5 inclusive the dampening cylinder I5 is shown as provided with a raised moisture carrying surface or design II for transferring the moisture to the areas on the offset cylinder which are not to receive the ink from the printing cylinders. In these figures the printing cylinders are shown as provided with raised ink carrying surfaces or designs I8 and I9 so related to each other and to the raised moisture carrying surface I! of the dampening cylinder I5 as to transfer the ink to those areas of the offset cylinder which have not been moistened by the said raised moisture carrying surface of the dampening cylinder.

As a preliminary step to the web offset printing operation, offset developing ink may be applied to the printing cylinders and transferred thereby to the offset cylinder until the designs have been created thereon. The moistening agent may then be applied to the offset cylinder to maintain the design contour. The offset printing on the web may then be started.

As the web offset printing operation proceeds the offset cylinder is moistened and then the color printing cylinders act successively to apply the ink to the offset cylinder. The offset cylinder will then simultaneously transfer the ink successively received from the several printing cylinders to the traveling web. This operation is repeated each revolution of the offset cylinder.

It will be understood that when the dampening cylinder is provided with raised moisture carrying surfaces and the printing cylinders with raised ink carrying surfaces the moisture and the colors are transferred to the offset cylinder so as to form a continuous surface consisting of separate moisture carrying and ink carrying areas to be transferred to the web by the offset cylinder.

When the moisture carrying surface of the dampening roll I5 is smooth the moisture carried thereby is applied uninterruptedly to the 3 entire surface of the offset cylinder 1 instead of only predetermined areas thereof. However, as the inks of the ink carrying areas of the offset cylinder are moisture repelling, due to the initially applied developing ink, no moisture will be transferred to these areas. I

While I have shown in the accompanying drawings five printing cylinders for applying color designs or patterns to the offset cylinder to be transferred to the traveling web it is to be understood that any number of printing cylinders may be used without departing from the spirit and scope of myinvention.

It will also be understood that the circumference of the offset cylinder must be an exact multiple of the circumference of the printing cylinders in order to make the design of these printing cylinders fit the circumference of their offset cylinder In the present instance the circumference of the offset cylinder is shown as four times the circumference of the printing cylinders.

It will also be understood that the ink carrying surfaces of the printing cylinders may be of any well known or approved form.

It is evident that various changes may be resorted to in the construction, form and arrangement of the several parts without departing from the spirit and scope of my invention, and hence I do not intend to be limited to the particular embodiment herein shown and described, but what I claim is:

1. In a web offset rotary printing press, an offset cylinder, a dampening cylinder having raised moisture carrying surfaces for applying moisture directly to the offset cylinder, a printing cylinder having raised ink carrying surfaces, and an inking cylinder for applying ink thereto, the said raised moisture and ink carrying surfaces being relatively positioned to produce a continuous film on the offset cylinder consisting of separate moistened and inked areas to be transferred thereby to the web.

2. In a web offset multicolor non-perfecting rotary printing press, an offset cylinder, an impression cylinder coacting therewith to pass the web between said cylinders, a dampening cylinder anda plurality of color printing cylinders arranged around the offset cylinder, said dampening cylinder having raised moisture carrying surfaces for applying moisture directly to the offset cylinder, said color printing cylinders having raised ink carrying surfaces, and a plurality of color inking cylinders for applying the inks to the raised ink carrying surfaces of their respective color printing cylinders, the said raised moisture and ink carrying surfaces being positioned to produce a continuous film on the offset cylinder consisting of separate moistened and inked areas.

3. The method of offset printing on one side of a traveling web consisting in applying moisture to the raised moisture carrying surfaces of a dampening cylinder, transferring the moisture therefrom to predetermined areas of the surface of an offset cylinder, applying ink to the complementary raised ink carrying surfaces of a printing cylinder, transferring the ink therefrom to the remaining areas of the surface of the offset cylinder to produce a continuous film thereon consisting of separate moistened and inked areas and transferring the ink designs from the offset cylinder to the traveling web.

4. The method of offset printing in multicolor on one side of a traveling web, consisting in applying moisture to the raised moisture carrying surfaces of a dampening cylinder, transferring the moisture therefrom to predetermined areas of the surface of an offset cylinder, applying ink to the complementary raised ink carrying surfaces of a plurality of color printing cylinders, successively transferring the ink therefrom to the remaining areas of the surface of the offset cylinder to produce a continuous film thereon consisting of separate moistened and inked areas, and transferring the ink designs from the offset cylinder to the traveling web.

HANS J. LUEHRS.

REFERENCES CITED The following references are of record in the 

